The purpose of this pilot is to determine the in vivo penetration of clarithromycin, an FDA-approved antibiotic, into peripheral blood leukocytes in order to improve its use in the treatment of intracellular infections. Clarithromycin will be administered orally as a single dose to 6 subjects. Blood will be drawn at 6 and 24 hrs following drug adminstration. The concentration of drug in peripheral blood monocytes will be determined using Ficoll-Hypaque separation and column chromatography.